O1123: Remote Ischemic Conditioning Improves the Survival and the Cognitive Behavior in Experimental Neonatal Sepsis

Background: Sepsis is characterized by systemic inflammation and remains one of the leading causes of morbidity and mortality in neonates. In neonates with severe sepsis, the systemic inflammatory response can induce multiple organ dysfunction, death or can result in long-term neurological deficits. Recently, we reported that a simple maneuver called remote ischemic conditioning (RIC) improved survival in experimental necrotizing enterocolitis and reduced cognitive behavior impairment post-injury of the survivors. RIC is characterised by transient and brief inflation and deflation of a pressure cuff, such as an extension of blood pressure measurement and is well tolerated in neonates. We hypothesize that RIC improves the survival and long-term cognitive behavior in neonatal experimental sepsis.

Methods: Sepsis was induced in C57BL/6 mouse pups on a postnatal day 9 by intraperitoneal injection of lipopolysaccharide (LPS 20 mg/kg). RIC, applied at the time of sepsis induction, consisted in 4 cycles of 5 minutes of hind limb ischemia by inserting a tourniquet followed by 5 minutes of reperfusion. Three groups of neonatal mice (normal control n=10; sepsis LPS alone n=17; and sepsis LPS+RIC n=6) were studied and monitored until death. The cognitive behaviour of the survivors was evaluated 3-months later. First, a three-chamber social recognition test involving: A) a habituation stage whereby a mouse explored two empty cages for 10 mins; B) Stage 2, which included a 5 min sociability test with an unencountered stranger mouse (S1) and one empty cage, and C) Stage 3, a 5 min social memory test with the previously encountered stranger (S1) and a second novel stranger (S2). Data were analyzed as a percentage time spent investigating the target cage over the total time interacting with either cage. Second, a short-term spatial memory water maze test consisting of A) a hidden stage; where mice placed in a pool of water were allowed to find the goal platform, and B) a probe test stage (2 hours post-training), mice were assessed again by measuring the time taken to reach the target quadrant versus other quadrants in the pool.

Results: Only 35% (6/17) septic mice survived sepsis compared to the totality of normal controls (10/10). RIC significantly improved the survival rate to 83% (5/6; p=0.0473) (Figure A). The social memory of surviving septic mice was impaired, but it was rescued by RIC treatment (Figure B). Furthermore, septic mice exhibited short-term spatial memory behavioral deficit which was rescued by the RIC treatment (Figure C).

Conclusion: Remote ischemic conditioning improves survival in neonatal experimental sepsis and improves long-term cognitive behavior of the survivors. These novel observations, coupled by the simplicity of remote ischemic conditioning, open the way to evaluate the effectiveness of this maneuver in the clinical setting of neonates with severe sepsis.